Heat exchangers, pre-heaters, economizers and the like



Feb. 1, 1966 E. s. A. ANDERLSSON ET AL 3,23 ,344

. q PR Filed July 19, 1963 2 Sheets-Sheet 1 Feb. 1, 1966 E. s. A. ANDERSSON E 3,232,344

HEAT EXCHANGERS, FEE-HEATER, ECONOMIZERS AND THE LIKE Filed July 19, 1963 2 Sheets-Sheet 2 United States Patent 3,232,344 HEAT EXCHANGERS, PRE-HEATERS, EQUNUMIZERS AND THE LIKE Erik Sven Alvar Andersson, Orrstigen l2, and Uno Sven Johnson, Jarpstigen 7, both of Sodertalje, Sweden Filed July 19, 1963, Ser. No. 296,312 Claims priority, application Sweden, July 20, 1962, 8,091/62 Ciaims. (Cl. 165-156) The present invention relates to heat-exchangers, preheaters, economizers and similar apparatus in which a heat-absorbing or heat-delivering medium flows through a space in which one or more heat transfer elements are disposed solidly secured to at least one wall defining said space.

A general object of the invention is to provide a heat transfer element of a design which is new in its context and which makes it possible to utilize said element also for the purpose of guiding, or controlling, the flow of said medium.

A special object of the invention is to provide a heat transfer element of such a shape that one branch of said medium flow can pass inside the element.

A further object of the invention is to provide a heat transfer element permitting great variations as to the proportion between that branch of the medium flow, which passes inside the element, and that branch, which passes outside.

A still further object of the invention is to provide a heat transfer element which on the one hand is cheap per se and, on the other, can in a rapid and cheap way be fixed to said wall, such as through automatic welding, so that the manufacture costs of the complete apparatus become compartively low.

The above-mentioned as well as further objects and advantages of the invention will become apparent from the following description when read in conjunction with the accompanying drawing, in which:

FiGURE 1 shows a heat transfer element according to a first embodiment of the invention.

FIGURE 2 shows a heat transfer element according to a second embodiment of the invention.

FIGURES 3a and 3b illustrate two ditferent ways of mounting a heat transfer element according to FIGURE 2.

FIGURE 4 is a fragmentary, sectional, perspective view showing a portion of a heat exchanging apparatus provided with heat transfer elements according to FIGURE 1.

FIGURE 5 illustrates the mounting of a heat transfer element according to FIGURES 2 and 3.

Reference numeral 1 designates a wall defining a space in e.g., a pre-heater, an economizer or some similar heatexchanging apparatus through which space there flows a heat-absorbing or heat-delivering medium. On said wall 1 there are mounted a number of heat transfer elements 2. According to the embodiment shown in FIGURE 1 these elements are constituted by pipes provided with substantially opposed or transverse holes, or perforations 3, while, according to the embodiment illustrated in FIGURE 2, each heat transfer element is constituted by a wire helically wound to a tube-like body. It is normally assumed that a wall corresponding to wall 1 is in close contact with the heat transfer elements at the opposite side thereof as shown in FIGURES 4 and 5. However, for the sake of surveyability no such wall has been shown in FIGURES 1 and 2.

It is understood that if a heat-absorbing or heat-delivering medium passes through the pipe-like members 2 shown in FIGURES 1 and 2 a portion of the medium in question will flow in the longitudinal direction of these members whereas another portion will flow transversely,

namely through holes 13 or through the spaces between the individual winding turns of the wire, respectively. It follows therefrom, that by variation of the area and the spacing of the holes and of the pitch and the wire diameter, respectively, it is possible to control the proportion between these two branches of the flow. In other words, elements 2 have been allotted two functions, i.e. they serve on one hand as heat transfer elements and, on the other, as means for controlling the medium flow.

The heat transfer element shown in FIGURE 2 and consisting of a helically wound wire is, as appears from that figure, somewhat flattened towards its longitudinal axis. Especially if this flattening is comparatively great, so that the loop-like portions at each of the two longitudinal sides of the element, where the individual winding turns meet, have a substantially greater radius of curvature at the one side than at the opposite one, it is an essential advantage that the joint between the element and the one of the two walls, the effective surface of which is increased by the element, is located at that side of the element, where the loops have the smaller radius of curvature. The significance of that feature appears from FIGURE 5, in which element 2 accordingly is fixed to wall 1, e.g. through welding. It is also apparent that a special advantage resides in the possibility of obtaining a continuous Welding joint which, in turn, permits the use of automatic or semi-automatic welding. From a comparison between FIGURES 3a and 3b it appears that the mounting rule just specified is of particularly great value when the helically wound element is to be attached to a curved wall, eg to the outer side of the tube in generally the way illustrated in FIGURE 4.

FIGURE 4 shows a portion of an apparatus, eg a heat-exchanging, in which the heat-delivering medium flows inside the element 2 whereas the heat-absorbing medium passes inside the big tube 1. From the above specification and from the drawings follows that thanks to the presence of holes 3 there is formed a short circuit passage for a portion of the flow which portion will pass vertically from one of the pipe turns 2 to an adjacent turn whereas the major portion of the medium still flows helically inside pipes 2. However, as has already been mentioned, it is possible within very wide limits to vary the proportion between these two branches of the medium flow. Numeral 4 in FIGURE 4 designates the outer wall, or jacket, of the heat-exchanger.

When a heat transfer element according to FIGURE 2 is arranged in the space between two co-axial tubes and the medium in question is supplied at the one end of said space and delivered at the other end, the winding turns of the wire may be located in planes which are either substantially axial or radial with respect to the co-axial tubes.

Finally, it should be emphasized that the purpose of this description and the drawing is only to exemplify the broad inventive concept which accordingly may be defined as suggesting the use of a heat transfer element of such a design that it could also be used to control the flow of the medium in question. It follows therefrom that the element can be designed in several other ways, e.g., consist of link-like members.

What is claimed is:

1. An apparatus for facilitating heat exchange between two fluids, comprising:

(a) an elongated first tube adapted to carry a first fluid axially therethrough;

(b) an elongated second tube, larger than said first tube and mounted to surround said first tube and form and annular space between said first and second tubes; and

(c) at least one pipe helical'ly disposed within and essentially filling said annular space;

(d) said helical pipe being in intimate heat exchange contact with the exterior Wall of said first tube; and

(e) said helical pipe having formed therein a plurality of substantially opposed perforations at spaced intervals along its length, whereby said helical pipe is adapted to carry a second fluid along a helical path through said helical pipe and along a second path, through said perforations, essentially parallel to the axes of said first and second tubes.

2. An apparatus in accordance With claim 1 wherein the size and number of the perforations in the helical pipe are selected to pass a major portion of the second fluid along the helical path.

3. An apparatus in accordance with claim 1 wherein a plurality of helical pipes are arranged in the annular space in generally concentric roWs and said helical pipes are in intimate heat exchange contact with one another and with the exterior Wall of the first tube.

4. An apparatus in accordance With claim 1 wherein References Cited by the Examiner UNITED STATES PATENTS 10/1943 Sterick 165l84 FOREIGN PATENTS 2/1951 France. 7/ 1931 Germany.

ROBERT A. OLEARY, Primary Examiner.

CHARLES SUKALO, Examiner.

20 A. W. DAVIS, Assistant Examiner. 

1. AN APPARATUS FOR FACILITATING HEAT EXCHANGE BETWEEN TWO FLUIDS, COMPRISING: (A) AN ELONGATED FIRST TUBE ADAPTED TO CARRY A FIRST FLUID AXIALLY THERETHROUGH; (B) AND ELONGATED SECOND TUBE, LARGER THAN SAID FIRST TUBE AND MOUNTED TO SURROUND SAID FIRST TUBE AND FORM AND ANNULAR SPACE BETWEEN SAID FIRST AND SECOND TUBES; AND (C) AT LEAST ONE PIPE HELICALLY DISPOSED WITHIN AND ESSENTIALLY FILLING SAID ANNULAR SPACE; (D) SAID HELICAL PIPE BEING IN INITIMATE HEAT EXCHANGE CONTACT WITH THE EXTERIOR WALL OF SAID FIRST TUBE; AND (E) SAID HELICAL PIPE HAVING FORMED THEREIN A PLURALITY OF SUBSTANTIALLY OPPOSED PERFORATIONS AT SPACED INTERVALS ALONG ITS LENGTHS, WHEREBY SAID HELICAL PIPE IS ADAPTED TO CARRY A SECOND FLUID ALONG A HELICAL PATH THROUGH SAID HELICAL PIPE AND ALONG A SECOND PATH, THROUGH SAID PERFORATIONS, ESSENTIALLY PARALLEL TO THE AXES OF SAID FIRST AND SECOND TUBES. 